A conventional dispensing system for supplying heated adhesive (i.e., a hot-melt adhesive dispensing system) generally includes an inlet for receiving adhesive materials in solid or semi-solid form, a melter in communication with the inlet for heating and/or melting the adhesive materials, an outlet in communication with the melter for receiving the heated adhesive from the melter, and a pump in communication with the melter and the outlet for driving and controlling the dispensation of the heated adhesive through the outlet. One or more hoses or manifolds may also be connected to the outlet to direct the dispensation of heated adhesive to adhesive dispensing guns or modules located downstream from the pump. Furthermore, conventional dispensing systems generally include a controller (e.g., a processor and a memory) and input controls electrically connected to the controller to provide a user interface with the dispensing system. The controller is in communication with the pump, melter, and/or other components of the dispensing system, such that the controller controls the dispensation of the heated adhesive.
One conventional type of hot-melt adhesive dispensing system may include a piston pump that operates by reciprocating a pump rod through forward and backward strokes in a hydraulic passage. For example, the pump rod may cause drawing of adhesive from a pump inlet into the hydraulic passage during a backward stroke and then force that adhesive from the hydraulic passage through a pump outlet during a forward stroke of the pump rod. The pump rod may also operate to push adhesive through the hydraulic passage during both the forward and backward strokes in some embodiments. The pump rod is connected to a piston in a piston chamber separated from the hydraulic passage, and the piston is driven in opposing directions by pressurized air delivered by solenoids into the piston chamber. As a result of the pump being driven at various speeds as well as continuously and intermittently, the pump must also include a shifter that reverses the movement direction of the piston and the pump rod when the pump rod reaches an end condition.
One particular type of shifter is a mechanical shifter that includes a magnet that moves with a portion of the pump rod. Corresponding switch magnets can be positioned adjacent the end conditions such that when the piston and pump rod arrive at an end condition, the magnet on the pump rod attracts or repels the switch magnet at that end condition to mechanically switch the solenoids to an opposite operating state. To this end, if a first solenoid supplying pressurized air to an upper side of the piston were active and a second solenoid supplying pressurized air to a lower side of the piston were inactive, the resulting movement of the switch magnet at the end condition would cause the first solenoid to be inactive and the second solenoid to be active. Consequently, the piston and pump rod would begin to move in the opposite direction towards the other end condition (at which point, the other switch magnet would mechanically switch the solenoids back to the original operating state). In similar embodiments, the solenoids may be replaced by an air shifting valve supplied with pressurized air, the air shifting valve being moved by the switch magnet to different positions to supply the pressurized air selectively to the upper and lower sides of the piston. The mechanical shifter is highly reliable in operation, but the various components and magnets must be carefully aligned within the pump to ensure proper operation of the pump.
Furthermore, pumps can develop various conditions such as leaking seals or inoperative valves that interfere with the pumping operation. Conventional piston pumps typically do not include sensors or monitoring devices that can detect these conditions, and therefore, the pumps must usually be damaged or significantly degraded before there is any indication that something is wrong with the pumps. To this end, the pumps are generally operated blindly with respect to these various conditions. Although diagnostics are conducted at the end of a manufacturing line for these pumps, the conventional pumps are inoperable to perform similar diagnostics when operating in the field. As a result, repairs of the pump can be time-consuming and costly (specifically, in lost production time or downtime caused by the repairs) when one of these various conditions occurs and interferes with the pumping operation.
For reasons such as these, an improved adhesive dispensing system and method, including the use of a pump with integrated diagnostics for use during regular operation, would be desirable.